1. Field of the Invention
The invention relates in general to pointers for dials or displays and more particularly to a snap-together pointer assembly with a one-piece hub device for securing the pointer to the display and preventing light leakage onto the display.
2. Discussion of Related Art
Prior art FIG. 1 illustrates a typical, three-part pointer and hub assembly, enlarged for clarity. A light shield 12, usually made of an opaque plastic, is formed with a hollow pointer stem 14 for fitting around a drive shaft of a stepper motor used to rotate the pointer and hub assembly. The light shield 12 has two spaced apart apertures 16 and a wider, semi-rectangular opening 18. A separate pointer blade 20, often made of a clear or transparent plastic, has a mounting section 22. The mounting section 22 has a light pick-up area or projection 24 extending from an underside 26 of the mounting section. A periphery of the light pick-up area 24 has the general shape of the opening 18 in the light shield 12. The mounting section 22 has two through-holes 28 about the same size as, and spaced apart the same distance as, the apertures 16 in the light shield 12. A detached, opaque cover or cap 30 is also made from plastic. The cap has a slot 32 similar in width and depth to the shape of the pointer blade 20 where the pointer blade 20 joins the mounting section 22.
As shown in FIG. 2 by a view of the bottom of the completed assembly, the interior of the cap 30 has two spaced apart posts 34 positioned to extend through the apertures 16 in the light shield 12 and the through-holes 28 in the mounting section 22 of the pointer blade 20. The light pick-up area 24 on the underside 26 of the mounting section 22 fits into and extends through the opening 18 in the light shield 12. Protruding ends of the posts 34 are crushed or melted in a heat staking process against an underside of the light shield 12 to hold the three parts together. The pointer stem 14 of the completed assembly then receives a stepper motor drive shaft in an interference or press fit so the pointer blade 20 can be moved about a dial or display to indicate appropriate measured values or parameters. The light pick-up area 24 transmits light from a light source (not shown) directly to the pointer blade 20 while the light shield 12 prevents light from being reflected back onto the display.
The prior art assembly requires three separate parts and a heat staking or similar process to secure the parts together. Reducing the number of parts and replacing the attachment process with a less expensive method would significantly decrease the cost and assembly time in a large volume production.